Avoiding redundant sound processing when using bluetooth

[jemenfous]

Hello All.

I am using PA to stream music via bluetooth to my car head unit using AAC codec.

I see the audio info and it shows a long arrow of digital processing, and I am trying to avoid unnecessary conversions as much as possible keeping quality and using EQ with DVC (which I need either for car playing and headphones). I can provide a picture later of the sound processing arrow.

 

I have some questions to improve my audio quality:

- If I am using DVC, do I have to put a specific value in Headroom (how values should be in "Headroom gain for DVC?).

- Using DVC prevents the overload or clipping when using EQ a bit too much? (let's say 4 db in certain frequencies) (should I use preamp with -4 db for instance?)

- Should I use float32 when using DVC, EQ via bluetooth? Does it makes sense? (using AAC bluetooth codec in standard settings, which are 16 bits, 256 kps 48khz).

 

Many thanks.

 

* I have PA language set in spanish, so options mentioned above might be slightly different in English, I hope you understand.

* I dont use android car, I just stream the music direct to car's head unit as a conventional bluetooth receiver.

[maxmp]

@jemenfous Hello and welcome to the forum

• the option is called "No DVC Headroom Gain" and it basically applies negative preamp to allow equalization in No DVC mode. Negative preamp is generally required for applying sound processing on normalized digital signal, where signal peaks already reach maximum digital value, so any direct amplification over that value is not possible (it will cause audible overloads and/or force Limiter to act, which causes rapid volume drops around loud parts of the signal). This is applied in non-DVC mode only
• DVC allows for more headroom (meaning we can amplify frequencies without negative preamp or overloading/limiting)
• float32 may work or may not work on the specific device/firmware/patch level. It's not possible to know that in advance, but you can try to enable it. It usually works on Pixel and Samsung devices, but often broken on the Chinese devices/firmwares

Thanks!

[jemenfous]

@maxmp thanks for the quick and good answer.

Just to add the audio info  as promised, so you can see if there is any conversion / resampling / recoding being redundant in the process.

Feel free to do propositions for changes / improvements on this settings. This sounds good, but there is always room for improvement.

Thanks.

 

* Sorry it's in Spanish.